Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors
Broad Applicability of Electrochemical Impedance Spectroscopy to the Measurement of Oxygen Nonstoichiometry in Mixed Ion and Electron Conductors
复制标题
电化学阻抗谱在混合离子和电子导体中氧非化学计量测量的广泛适用性
DOI：
10.1021/acsami.2c05417
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发表时间：
2022
影响因子：
9.5
通讯作者：
Haile, Sossina M.
中科院分区：
文献类型：
--
作者：
Huang, Ruiyun;Carr, Connor G.;Gopal, Chirranjeevi Balaji;Haile, Sossina M.
氧非化学计量是混合离子和电子导体的一个基本特征。在这项工作中，展示了一种通过测量化学电容来确定薄膜miec非化学计量学的通用电化学方法，该方法以二氧化铈和二氧化铈（Ce0.8Zr0.2O2−δ）为代表材料。交流阻抗数据是在高温（750-900°C）和还原条件下收集的，氧分压（pO2）范围为10 - 13至10-20atm。在相对氧化的条件下，po2在0.2至10-4atm范围内，温度为800-900℃，对铈锆薄膜进行了额外的测量。在还原条件下，阻抗谱由一个简单的电路描述，其中电阻串联，电阻和电容并联，并使用与厚度相关的测量来将电容分解为界面和化学术语。在更多氧化条件下，Ce0.8Zr0.2O2−δ的阻抗谱显示出额外的扩散特征，这使得除了电容之外，还可以确定膜的离子电阻，从而确定输运性质。本文提出了一种广义的数学形式，用于从化学电容中恢复非化学计量，而不依赖于缺陷化学模型。铈的非化学计量值与文献中由热重测量确定的值很好地一致，但显示出相当小的散射，并且在相当短的时间尺度上收集。Ce0.8Zr0.2O2−δ的热力学分析证实了早先的发现，即在铈中引入Zr增强了其还原性。
Oxygen nonstoichiometry is a fundamental feature of mixed ion and electron conductors (MIECs). In this work, a general electrochemical method for determining nonstoichiometry in thin film MIECs, via measurement of the chemical capacitance, is demonstrated using ceria and ceria-zirconia (Ce0.8Zr0.2O2−δ) as representative materials. A.C. impedance data are collected from both materials at high temperature (750–900 °C) under reducing conditions with oxygen partial pressure (pO2) in the range 10–13to 10–20atm. Additional measurements of ceria-zirconia films are made under relatively oxidizing conditions withpO2in the range 0.2 to 10–4atm and temperatures of 800–900 °C. Under reducing conditions, the impedance spectra are described by a simple circuit in which a resistor is in series with a resistor and capacitor in parallel, and thickness-dependent measurements are used to resolve the capacitance into interfacial and chemical terms. Under more oxidizing conditions, the impedance spectra (of Ce0.8Zr0.2O2−δ) reveal an additional diffusional feature, which enables determination of the ionic resistance of the film in addition to the capacitance, and hence the transport properties. A generalized mathematical formalism is presented for recovering the nonstoichiometry from the chemical capacitance, without recourse to defect chemical models. The ceria nonstoichiometry values are in good agreement with literature values determined by thermogravimetric measurements but display considerably less scatter and are collected on considerably shorter time scales. The thermodynamic analysis of Ce0.8Zr0.2O2−δcorroborates earlier findings that introduction of Zr into ceria enhances its reducibility.